The objective of the Imaging Core at Memorial Sloan-Kettering Cancer Center (MSKCC) is to provide individual projects with unique capabilities for detecting, localizing, and biologically characterizing primary and metastatic breast cancer cells in vivo. This will be accomplished primarily through non-invasive imaging techniques such as gamma camera imaging and positron emission tomography (PET) of radiolabeled tracers, magnetic resonance imaging (MRI), and optical imaging of bioluminescent luciferase-reactive reporter substrates and imaging GPF reporter fluorescence. These non-invasive in vivo techniques are supplemented by and validated with standard molecular biological techniques (e.g., RT-PCR, Western blot, immunohistochemistry, etc); techniques such as phosphor-plate digital autoradiography and liquid and solid-state scintillation counting will supplement radiotracer-based imaging techniques. Results in experimental animals may be directly transferable to human studies using currently available clinical imaging facilities at MSKCC, includingPET and MRI.